Cooling system

ABSTRACT

A cooling system ( 100 ) for an engine ( 150 ), comprising at least one coolant pump ( 120 ) for pumping a coolant through the engine ( 150 ) and a thermostat ( 140 ) operable to selectively direct said coolant from said engine ( 150 ) via a bypass ( 115 ) back to said engine ( 150 ) or via a main radiator ( 110 ) back to said engine ( 150 ) in response to a temperature of said coolant from said engine ( 150 ), and an expansion vessel ( 130 ) for deaerating said cooling system ( 100 ). The system (100) includes a first deaeration conduit ( 13 V) connecting a high point of said engine ( 150 ) to said expansion vessel ( 130 ), and a second deaeration conduit ( 138 ′) connecting a high point of said main radiator ( 110 ) to said expansion vessel, and said first and second deaeration conduits ( 137′, 138 ′) are provided with at least one heat exchanger ( 145, 145 ′) for cooling coolant flowing through said deaeration conduits ( 137′, 138 ′).

BACKGROUND AND SUMMARY

The present invention relates to a cooling system for an engine. The system comprises a main radiator, at least one coolant pump, an expansion vessel, and at least one deaeration conduit connecting at least one high point of the cooling system and the expansion vessel.

Today, most cooling systems for engines in trucks, heavy duty trucks, tractors, passenger cars, marine engines, excavators etc. are equipped with so called deaeration systems, i.e. a (small diameter) hose or pipe leading from a high point of the cooling system to the expansion vessel. As is well known by persons skilled in the art, gas tends to cumulate in high points in cooling systems, and by providing a hose or pipe leading from a high point to the expansion vessel, cumulated gas will enter the expansion vessel, where the gas can be separated from coolant by the force of gravity.

For a number of reasons, it is more or less industry standard to use expansion vessels made from transparent plastic material; a transparent material gives a possibility to monitor both the coolant level and the condition of the coolant by noticing colour changes.

In the automotive industry, there is an ongoing trend towards ever higher coolant temperatures. Higher coolant temperatures mean a lot of advantages; for example, the main radiator can be significantly smaller, still maintaining a cooling rate which is high enough.

The higher coolant temperature is however not only beneficial; a side effect of the higher coolant temperature is that the life of the expansion vessel is significantly reduced. One way of improving the life is to manufacture the expansion vessel of a more temperature durable material, but this has proven to be expensive.

According to an aspect of the present invention at least one secondary heat exchanger is provided for cooling coolant flowing through said at least one deaeration conduit.

In a preferred embodiment of the invention, the at least one secondary heat exchanger is an elongate pipe or hose placed in a stream of air. This embodiment is advantageous in that it is uncomplicated and inexpensive.

The first embodiment can be further improved if the elongate pipe or hose is provided with area increasing means. This allows for a shorter pipe or hose.

In another embodiment, the secondary heat exchanger is a coolant/coolant heat exchanger exchanging heat between a cold coolant and the coolant flowing through said at least one deaeration conduit. This embodiment could be useful if the vehicle is equipped with separate cooling circuits for engine and appliances, e.g. gearbox and/or charge cooler.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described with reference to the appended drawings, wherein: FIG. 1 is a schematic view of a first embodiment of the present invention, and FIG. 2 is a schematic view of a second embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a cooling system 100 according to the present invention, wherein the cooling system 100 is intended to cool an engine 150. The cooling system 100 comprises a main radiator 110, a bypass 115, a coolant pump 120, an expansion tank 130 provided with a filler cap 131, inlets 137, 138 and an outlet 139 situated at a bottom part of the expansion tank, a thermostat 140 and secondary heat exchangers 145, 145′. The outlet 139 is connected to a point downstream the radiator 110 and upstream the coolant pump 120 by a conduit 180 (for definition of upstream and downstream, see next paragraph). Moreover, the cooling system 100 includes first and second drain cocks 160, 161 located at bottom portions of the main radiator 110 and an engine 150 to be cooled, respectively. In some embodiments, the cooling system is connected to a gearbox cooler 170 and/or a brake compressor 175, i.e. the compressor for supplying the braking system of the vehicle with compressed air.

As is well known by persons skilled in the art, the above mentioned components are interconnected by a hosing and/or piping system, which in FIG. 1 are shown as full lines provided with small arrows indicating a flow direction of a coolant flowing between the above mentioned components. Consequently, a side of a component facing a tip of a small arrow is an upstream side of the component, and a side of a component facing a base of the small arrow is a downstream side of said component. The hosing and/or piping system is only given reference numerals when a portion of the system is directly referred to, since the basic function of such a system is well known by persons skilled in the art.

Two deaeration conduits 137′, 138′ connect high points in the cooling system 100 on the engine 150 and on the main radiator 110 to the inlets 137, 138 of the expansion vessel, via the secondary heat exchangers 145, 145′, respectively.

Hereinafter, the function of the cooling system 100 will be described with reference to FIG. 1. The purpose of the cooling system is mainly to cool the engine by transferring heat from the engine 150 to the main radiator 110. The coolant pump 120 provides the flow of coolant, the direction of which, as mentioned earlier, being indicated by small arrowheads on the conduits connecting various components, into internal cooling circuits CC in the engine 150, where the coolant absorbs heat, which increases the temperature of the coolant. After having collected the heat in the engine, the coolant passes the thermostat 140; if the coolant temperature is above a threshold value, e.g. 110 degrees centigrade, the thermostat directs the flow of coolant to the main radiator 110, where the hot coolant exchanges heat with ambient air. The heat exchange with the air results in a temperature drop of the coolant. After the radiator, the cold coolant is again fed to the coolant pump 120, from which it again enters the engine's coolant circuits CC.

If the temperature of the coolant after having passed the engine's coolant circuits is lower than the threshold value, the coolant is directed by the thermostat 140 to the bypass 115, in order to let the coolant bypass the main radiator 110. Hence, the coolant experiences no significant temperature drop, which helps the coolant, and hence the engine, to reach an appropriate working temperature more rapidly. If the temperature is close to the threshold value, the thermostat might direct part of the coolant flow through the radiator, and allow the other part of the coolant flow to bypass the main radiator.

In order to deaerate the coolant, the two deaerating conduits 137′, 138′ are connecting a point close to the thermostat 140 and a point on the top area of the main radiator 110 to the inlets 137 and 138 of the expansion vessel 130, respectively. During operation, coolant will be forced to flow through the conduits 137′, 138′ to the expansion vessel 130 due to the coolant pressure drop over the main radiator 110 or the bypass 115. The coolant entering the expansion vessel will eventually re-enter the cooling flow scheme coolant pump 120—engine 150—thermostat 140—main radiator 110. This re-entering takes place by the conduit 180 connecting the expansion vessel outlet 139 to a point downstream the main radiator 110 and upstream the coolant pump 120.

Since the thermostat 140 and the main radiator 110 represent two high points in the cooling system, the coolant flowing through the deaerating conduits may contain some gas, which e.g. might emanate from small leaks or simply from diffusion of combustion gas through the cast iron from which the engine is manufactured.

In the expansion vessel 130, which compared to the conduits 137′ and 138′ represents a large volume, the possible gas mixed in the coolant from the engine 150 and the main radiator 110 will raise towards the coolant surface, hence leaving a virtually gas free coolant to re-enter the cooling circuits CC of the engine 150.

According to the invention, the coolant temperature is decreased by the provision of the secondary heat exchangers 145, 145′, which as mentioned are placed in the deaeration conduits 137′, 138′.

According to a first embodiment of the invention, the secondary heat exchangers 145 and 145′ are simply elongate pipes of a heat conducting material, e.g. any kind of metal, e.g. iron, steel, copper, aluminium, stainless steel or any other suitable metal. In one embodiment, the pipes are placed in a stream of cold air, e.g. in front of the main radiator 110. In another embodiment of the invention, these pipes are provided with area increasing means, e.g. circumferentially extending wings.

In still another embodiment, the secondary heat exchangers might be coolant/coolant heat exchangers. This might be an advantageous solution if two separate cooling systems are used, e.g. one high temperature cooling system for cooling the engine and one low temperature cooling system for gearbox cooling. Separate cooling systems could also be used as a means for allowing a coolant/air heat exchanger as a charge cooler for engine intake air, compressed in the turbocharger, in a way that is well known by persons skilled in the art.

Furthermore, the invention has been described with two separate secondary heat exchangers 145, 145′. In another embodiment, it might be advantageous to omit one of such heat exchangers 145, 145′, or, such as shown in FIG. 2, to combine them into a single heat exchanger 200 cooling coolant emanating from either the top of the radiator or the top of the engine, or both.

As can be seen, most reference numerals have been omitted in FIG. 2, for the sake of simplicity. It is however obvious that all non-referenced components shown in FIG. 2 are identical to those shown in FIG. 1. 

1. A cooling system for an engine, the system comprising at least one coolant pump operable to pump a coolant through the engine, a thermostat operable to selectively direct the coolant from the engine via a bypass back to the engine or via a main radiator back to the engine in response to a temperature of the coolant from the engine, and an expansion vessel for deaerating the cooling system, at least a first deaeration conduit connecting a high point of the engine to the expansion vessel, and a second deaeration conduit connecting a high point of the main radiator to the expansion vessel, and the first and second deaeration conduits being provided with at least one heat exchanger for cooling coolant flowing through the deaeration conduits.
 2. A cooling system as claimed in claim 1, wherein the at least one secondary heat exchanger is an elongate pipe or hose placed in operation in a stream of air.
 3. A cooling system as claimed in claim 2, wherein the elongate pipe or hose is provided with area increasing means.
 4. A cooling system as claimed in claim 1, wherein the secondary heat exchanger is a coolant/coolant heat exchanger exchanging heat between a second coolant and the coolant flowing through the deaerating conduits. 